1. Technical Field
The present invention relates to an image processing device and method. More particularly, the present invention relates to an image processing device and method for measuring the coordinates of a photographing device or an object by keeping track of a dynamic image of the object taken when the photographing device moves relative to the object.
2. Related Art
There is known a technique to measure the position of a photographing device by continuously photographing an object while the photographing device is moving relative to the object. When the photographing device is actually mounted on a moving body such as a car or held in the hand of a person to perform photographing, however, the acquired images may occasionally be far from stable and require vertical or rotational corrections frame by frame, due to the sway of the car or the person. In some cases, a moving object such as another car or person, a flying bird or a falling leaf, may intervene between the photographing device and the object, causing feature points (this may referred to as characteristic points) to be hidden behind and reappear again. Movement in a three-dimensional (3D) space may occasionally be difficult to perceive when viewed on a two-dimensional (2D) image. Thus, there is a need for a process to deal with such sway of the photographing device, a process to deal with feature points that disappear and reappear, and a process to identify and delete feature points and corresponding points inappropriate for 3D measurement. On other hand, for the case where a stationary object is photographed with a stationary photographing device, there is disclosed a 3D measurement technique to precisely and automatically search for corresponding points for measurement. (See Patent Document 1.)
[Patent Document 1] JP-A-2003-264852 (paragraphs [0018] to [0073], FIGS. 1 to 11, etc.)
In order to measure the 3D coordinates of a photographing device or an object based on moving images, it is necessary to find, on two or more frames of the moving image, feature points corresponding to each other, or identical points on the object (hereinafter referred to “corresponding feature points”) and to keep track of them. In the case where movement is made in the depth direction of a 3D space when corresponding feature points are to be obtained, for example, such movement cannot be recognized as movement when viewed two-dimensionally. Rather, so-called “pseudo feature points” and “pseudo reference points”, which are recognized on the image at corners of two or more lines at different depth levels in the 3D space, prevent proper removal of erroneous corresponding points. Conventional analysis of a moving image is based on the evaluation of 2D movement of points, and not 3D movement thereof. Erroneous corresponding points that could not be properly removed consequently deteriorate the measurement precision of 3D coordinates and reduce the reliability of the measurement.
Thus, it is required to provide a technique that can precisely measure the photographing position and posture of a photographing device and the coordinates of an object from photographed images that sequentially change such as a moving image, even in the case where it is necessary to identify and delete feature points and corresponding points inappropriate for 3D measurement, by developing and applying the technique to photograph a stationary object with a stationary photographing device described above to the case where either or both of them are mobile.
The objective of the present invention is to provide an image processing device and method that can precisely measure the photographing position or posture of a photographing device or the coordinates of an object based on sequentially changing photographed images, such as moving images.